Electrochemical Characterization of Ni/Y2O3-ZrO2 Hydrogen Electrode for Water Splitting in Solid Oxide Electrolysis Cells

Ni-Y₂O₃ stabilized ZrO₂ (Ni-YSZ) cermet is a widely used hydrogen electrode for solid oxide fuel cells (SOECs), but detailed studies regarding the water splitting processes are scarce. Here we report the preliminary results on the electrocatalytic activity of Ni-YSZ hydrogen electrode in the SOEC mode as a function of operating temperature and water concentration. The electrode activity for the water splitting reaction is strongly influenced by the water concentration and dc bias. The electrochemical performance for the water splitting reaction increases with the increase of water concentration. On the other hand, the electrode polarization resistance increases gradually with the increase of dc bias regardless of the H₂O content, which is particularly pronounced in the low frequency impedance process related to the H₂O dissociative adsorption and diffusion processes. The reaction mechanism and kinetics of the H₂O dissociation reaction on Ni-YSZ hydrogen electrodes are discussed.